INFLUENCE OF MAST-CELLS ON 2 MURINE MAMMARY ADENOCARCINOMAS

A high content of mast cells (MC) is considered characteristic of neop lasias. Some researchers postulate MC as enhancers of tumor developmen t, others as inhibitors. The purpose of this study was to evaluate the ability of peritoneal cavity MC to modulate the in vivo and in vitro growth of two murine mammary adenocarcinomas with low (M3) and high (M M3) metastatic capacity. MC from the peritoneal cavity of normal (NMC) or tumor-bearing mice (TMC) were used. TMC, which by histochemical me thods appeared degranulated, were not able to modify the tumorigenicit y of both tumors. NMC, in contrast, decreased M3 tumor incidence and c ell proliferation in vitro and increased the latency period of only MM 3 tumors. No changes in the number of spontaneous lung metastases coul d be seen in experiments carried out either with NMC or TMC. We conclu de that NMC, which are rich in chemical mediators, can modulate some o f the first steps of tumor development. Once tumor-mediated degranulat ion occurs, MC become unable to regulate it.